1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive employing a multi-layer noise-damping HDA cover.
2. Description of the Prior Art
A computer system usually includes one or more disk drives for economical, non-volatile data storage. FIG. 1 shows a prior art disk drive 100 disclosed in U.S. Pat. No. 5,282,100 to Tacklind et al. which includes a housing formed by fitting a cover comprising an inner layer 102 and a outer layer 104 to a base 106 to create a sealed head disk assembly (HDA) chamber. The HDA includes one or more disks 108 stacked in a spaced-apart relationship on a spindle motor hub and rotated by a spindle motor (not shown). The spindle motor includes a stationary element such as a spindle journal fixed to the disk drive housing at the base and cover to define and stabilize a spindle axis about which the disks 108 rotate. The disks 108 rotate in close proximity to a read/write head 114 that is disposed by means of a head gimbal assembly (HGA) attached to one of a plurality of actuator arms 110.
The actuator arms 110 are part of a head stack assembly (HSA) that turns about a pivot bearing assembly. The pivot bearing assembly includes a stationary element such as a pivot journal that is fixed to the disk drive housing at the base and cover to define and stabilize a pivot axis for the HSA. Typically, the pivot bearing assembly and spindle motor journals are rigidly coupled at the top to the cover and at the bottom to the base, thereby fixing and stabilizing the relationship of the two axes to control head positioning error.
The actuator arms 110 move in response to energizing currents sent to a voice coil motor (VCM) 112 which moves the HSA on the pivot axis, swinging the actuator arms 110 to move the associated heads 114 over the associated disk surfaces. When moved in this manner during normal operation, the HSA tends to vibrate. The spindle motor, rapidly spinning the disks, contributes additional vibration. Vibration from the spindle motor and VCM 112 may be transmitted to the disk drive housing through the pivot and spindle journals. The resulting vibration in the housing causes radiation of acoustic noise, especially from the cover which, having a relatively large vibrating surface, may act like a speaker cone and produce undesirably high levels of acoustic noise.
The demand for increasingly higher data transfer rates to and from the magnetic surfaces of the disk 108 calls for increasingly higher disk rotation speed. However, as the disk rotation speed increases, even higher levels of undesirable acoustic noise are generated.
Referring again to the prior art disk drive of FIG. 1, the outer layer 104 of the HDA cover is attached to the inner layer 102 using a mechanical isolation and sound damping material, such as adhesive coated foam rubber, thereby isolating the outer layer 104 mechanically and acoustically from the inner layer 102. In this manner, the outer layer 104 and sound damping adhesive attenuate the acoustic noise that would otherwise emanate from the inner layer 102. However, as disk rotation speeds increase, further attenuation of acoustic noise is desirable, particularly for certain applications such as digital video recorders.
There is, therefore, a need to further attenuate acoustic noise emanating from a disk drive, particularly since increasing disk rotation speeds has amplified acoustic noise in prior art disk drives.
The present invention may be regarded as a disk drive with reduced acoustic noise comprising a disk, a head, an actuator arm for actuating the head radially over the disk, a base, and a cover attached to the base to form a head disk assembly chamber. The cover comprises an inner layer having a depression, the depression comprising a convex surface and a concave surface, an outer layer attached opposite the concave surface to the inner layer, the inner layer and the outer layer thereby defining walls of a cavity. The cover further comprises a damping medium disposed within the cavity, whereby the inner layer, the outer layer, and the damping medium form a multi-layer noise-damping sandwich which reduces noise emitted by the disk drive.
In one embodiment the damping medium comprises a metal weight. In an alternative embodiment, the damping medium further comprises an adhesive layer for securing the metal weight to at least one of the walls of the cavity. In yet another embodiment, the damping medium comprises compressed acoustic foam. In still another embodiment, the convex surface of the depression is positioned proximate the disk within the head disk assembly chamber for reducing air turbulence and windage drag.
The present invention may also be regarded as a method for manufacturing a disk drive with reduced acoustic noise. A depression is formed in an inner layer of a cover, the depression comprising a convex surface and a concave surface. An outer layer is attached opposite the concave surface to the inner layer, the inner layer and the outer layer thereby defining walls of a cavity. A damping medium is disposed within the cavity, whereby the inner layer, the outer layer, and the damping medium form a multi-layer noise-damping sandwich which reduces noise emitted by the disk drive. The inner layer of the cover is attached to a base to form a head disk assembly chamber.